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| United States Patent |
6,198,867
|
|
Yamamoto
, et al.
|
March 6, 2001
|
Radiation-curable liquid resin composition and optical fiber
Abstract
A radiation-curable liquid resin composition contains (A) an
organopolysiloxane having a (meth)acryl group at either end of its
molecular chain, containing at least 15 mol % of aromatic hydrocarbon
groups based on the entire organic groups, and being free of a urethane
bond, (B) a compound having at least one ethylenically unsaturated group
in a molecule, and (C) a photopolymerization catalyst. The composition has
a low viscosity and cures into a product having a low Young's modulus and
experiencing a less change of Young's modulus at low temperatures. The
composition is useful as a primary coating for optical fibers.
| Inventors:
|
Yamamoto; Akira (Gunma-ken, JP);
Kozakai; Shouhei (Annaka, JP);
Iwasaki; Satoshi (Gunma-ken, JP)
|
| Assignee:
|
Shin-Etsu Chemical Co., Ltd. (Tokyo, JP)
|
| Appl. No.:
|
339167 |
| Filed:
|
June 24, 1999 |
Foreign Application Priority Data
| Jul 08, 1998[JP] | 10-208656 |
| Current U.S. Class: |
385/128; 385/123; 385/141; 427/163.2; 427/487; 427/489 |
| Intern'l Class: |
G02B 006/02; C08F 002/46 |
| Field of Search: |
385/123,127,128,141,145
427/487,489,493,515,516,163.2
65/432
|
References Cited
U.S. Patent Documents
| Re33737 | Nov., 1991 | Hida et al. | 385/141.
|
| 4496210 | Jan., 1985 | Ansel et al. | 385/141.
|
| 4571349 | Feb., 1986 | Hockemeyer et al. | 427/54.
|
| 4733942 | Mar., 1988 | Hida et al. | 427/163.
|
| 4743474 | May., 1988 | Homan | 427/387.
|
| 4908274 | Mar., 1990 | Jachmann et al. | 428/452.
|
| 4972005 | Nov., 1990 | Aoki et al. | 522/99.
|
| Foreign Patent Documents |
| 61-21121 | Jan., 1986 | JP | 385/141.
|
| 2429619 | May., 1992 | JP | 385/141.
|
| 22522663 | May., 1996 | JP | 385/141.
|
| 22547021 | Aug., 1996 | JP | 385/141.
|
Other References
XP002117870, Chemical Abstracts, vol. 106, No. 20, May 18, 1987, Columbus,
OH, Abstract No. 157609.
|
Primary Examiner: Healy; Brian
Claims
What is claimed is:
1. A radiation-curable liquid resin composition comprising
(A) an organopolysiloxane having a (meth)acryl group at either end of its
molecular chain, containing at least 15 mol % of aromatic hydrocarbon
groups based on the entire organic groups attached to silicon atoms, and
being free of an urethane bond within the molecule,
(B) a compound having at least one ethylenically unsaturated group in a
molecule, and
(C) a photopolymerization catalyst.
2. The composition of claim 1 wherein the organopolysiloxane of component
(A) is a linear diorganopolysiloxane having (meth)acryloxyalkyl groups at
both ends of the molecular chain.
3. The composition of claim 1 wherein the organopolysiloxane of component
(A) is of the following formula (1):
##STR10##
wherein R.sup.1 is a hydrogen atom or a methyl group, R.sup.2 is
independently a substituted or unsubstituted monovalent hydrocarbon group
having 1 to 10 carbon atoms, R.sup.2 contains at least 15 mol % of
aromatic hydrocarbon groups, m is an integer of 1 to 5, and n is an
integer of 80 to 1,200.
4. The composition of claim 1 wherein the compound having at least one
ethylenically unsaturated group in a molecule of component (B) is an
organic silicon compound of the following formula (2):
##STR11##
wherein R.sup.1 is a hydrogen atom or a methyl group, and a is equal to 0
or 1.
5. The composition of claim 1 for use in the coating of optical fibers.
6. An optical fiber covered with a cured product of the composition of
claim 1.
Description
This invention relates to a radiation-curable liquid resin composition
which has a low viscosity and cures into a product having a low Young's
modulus and suitable as a primary coating or buffer layer on optical
fibers. It also relates to an optical fiber covered with a cured product
of the composition.
BACKGROUND OF THE INVENTION
Optical fibers for data communication include a variety of fibers such as
quartz glass, multi-component glass and plastic fibers. In practice,
because of their light weight, low loss, durability, and high transmission
capacity, quartz glass optical fibers are vastly used in a wide range of
application. Since the quartz glass optical fibers, however, are very thin
and susceptible to changes by external factors, quartz glass fibers as
melt spun are generally provided with a primary coating and then with a
secondary coating for protecting the primary coating. The primary coating
is formed by applying a liquid curable resin of the type giving a soft
cured product, followed by curing. The secondary coating is formed by
applying a liquid curable resin of the type giving a hard cured product,
followed by curing.
Properties required for the primary coating material include a low Young's
modulus and low temperature dependency thereof for preventing microbending
losses by external stresses or temperature changes, durability in terms of
heat resistance and water resistance, low water absorption, low hydrogen
generation, a high refractive index, and a fast-curing ability and low
viscosity for allowing the drawing speed of optical fibers to be increased
for improved productivity. To meet these requirements, UV-curable
compositions based on urethane acrylate were proposed in the past. For
example, JP-B 1-19694 and Japanese Patent Nos. 2,522,663 and 2,547,021
disclose liquid UV-curable compositions comprising a urethane acrylate
oligomer, a reactive monomer, and a polymerization initiator. These
compositions, however, fail to meet some of the above requirements, that
is, a low Young's modulus and good low-temperature properties (minimized
temperature dependency of Young's modulus), low water absorption, and low
viscosity, because they are based on urethane acrylate oligomers of
urethane bond-bearing polyethers or polyesters.
For reducing Young's modulus and improving low-temperature properties, JP-B
4-29619 corresponding to U.S. Pat. No. 4,496,210 and JP-A 61-21121
disclose liquid UV-curable compositions using a silicone urethane acrylate
containing an organic polysiloxane. Urethane bonds are contained likewise.
Because of the structural factors of urethane bonds (specifically,
rigidity of the structure and the hydrogen bond in the urethane bond),
these compositions are not satisfactory to some of the above requirements,
that is, a low Young's modulus and a low viscosity. The embodiments
described in these patents suggest that the organic polysiloxane is
limited to a dimethylsiloxane skeleton, which has a low refractive index
and is less compatible with reactive monomers. It is then difficult to
design a liquid UV-curable composition capable of satisfying the required
values.
SUMMARY OF THE INVENTION
An object of the invention is to provide a low-viscosity radiation-curable
liquid resin composition which cures into a product having a low Young's
modulus and experiencing a less change of Young's modulus at low
temperature. Another object of the invention is to provide an optical
fiber coated with a cured product of this composition.
The invention addresses a radiation-curable liquid resin composition
comprising a (meth)acryl group-bearing oligomer or polymer as a main
component. The inventor has found that an organopolysiloxane having a
(meth)acryl group at each end of its molecular chain, containing at least
15 mol % of aromatic hydrocarbon groups based on the entire organic groups
attached to silicon atoms, and being free of a urethane bond within the
molecule is fully compatible with a reactive monomer and when it is used
as the main component, the resulting radiation-curable liquid resin
composition has a low viscosity and cures into a product having a low
Young's modulus and a high refractive index. Especially when a monomer
based on an organosiloxane skeleton and having an ethylenically
unsaturated group is used as the reactive monomer, the cured product
experiences a minimal change of Young's modulus at low temperatures.
The invention provides a radiation-curable liquid resin composition
comprising (A) an organopolysiloxane having a (meth)acryl group at either
end of its molecular chain, containing at least 15 mol % of aromatic
hydrocarbon groups based on the entire organic groups attached to silicon
atoms, and being free of a urethane bond within the molecule, (B) a
compound having at least one ethylenically unsaturated group in a
molecule, and (C) a photopolymerization catalyst.
This composition is effective for the coating of optical fibers. Therefore,
an optical fiber covered with a cured product of the composition is also
contemplated herein.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
(A) Urethane Bond-free, (meth)Acryl Group-bearing Organopolysiloxane
The first component of the radiation-curable liquid resin composition
according to the invention is an organopolysiloxane which has a
(meth)acryl group at either end of its molecular chain, contains at least
15 mol % of aromatic hydrocarbon groups based on the entire organic
substituents attached to silicon atoms, and is free of a urethane bond
within the molecule; especially a linear diorganopolysiloxane containing
at least 15 mol % of aromatic hydrocarbon groups based on the entire
organic substituents (that is, substituted or unsubstituted monovalent
hydrocarbon groups) attached to silicon atoms, excluding the (meth)acryl
group-bearing organic groups attached to the silicon atoms at both ends of
the molecular chain. In the specification, (meth)acryl group means acryl
group and/or methacryl group.
This organopolysiloxane is the base polymer of the liquid resin composition
according to the invention and is basically a linear diorganopolysiloxane
whose backbone consists of recurring diorganosiloxane units. The number of
silicon atoms in the molecule (or the degree of the polymerization) is
generally about 80 to about 1,200, preferably about 100 to about 1,000.
Preferably the (meth)acryl group is attached to the silicon atom at each
end of the molecular chain as a (meth)acryloxyalkyl group.
Typically, the organopolysiloxane is represented by the following general
formula (1).
##STR1##
Herein R.sup.1 is a hydrogen atom or a methyl group, R.sup.2, which may be
the same or different, is a substituted or unsubstituted monovalent
hydrocarbon group having 1 to 10 carbon atoms, R.sup.2 contains at least
15 mol % of aromatic hydrocarbon groups, m is an integer of 1 to 5, and n
is an integer of 80 to 1,200, and preferably 100 to 1,000.
Formula (1) is described in detail. R.sup.1 is a hydrogen atom or a methyl
group, although the hydrogen atom is preferred when the curing rate of the
composition upon exposure to radiation is taken into account. R.sup.2
represents substituted or unsubstituted monovalent hydrocarbon groups
having 1 to 10 carbon atoms, preferably substituted or unsubstituted
monovalent hydrocarbon group having no aliphatic unsaturated bonds, for
example, straight, branched or cyclic alkyl groups of 1 to 10 carbon
atoms, especially 1 to 6 carbon atoms, aryl groups of 6 to 10 carbon
atoms, and aralkyl groups of 7 to 10 carbon atoms. Exemplary groups of
R.sup.2 are alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl,
isobutyl, tert-butyl, pentyl, hexyl, cyclohexyl, octyl, nonyl and decyl;
aryl groups such as phenyl, tolyl, xylyl, and ethylphenyl; aralkyl groups
such as benzyl, .beta.-phenylethyl, and .alpha.-methyl-.beta.-phenylethyl;
and substituted ones of these groups wherein some of the hydrogen atoms
are replaced by halogen atoms (e.g., F, Cl and Br), typically
halo-substituted alkyl groups such as chloromethyl, bromoethyl, and
3,3,3-trifluoropropyl. Methyl and phenyl groups are preferable from the
commercial aspect. For increasing the refractive index of the inventive
composition, it is desired to increase the compatibility of the
organopolysiloxane (A) with the monomer having at least one ethylenically
unsaturated bond in a molecule (B) as the second component of the
composition, especially an acrylic compound. To this end, aromatic
hydrocarbon groups are contained in an amount of at least 15 mol %,
typically 15 to 50 mol %, especially 15 to 30 mol %, based on the R.sup.2
groups. Exemplary aromatic hydrocarbon groups are aryl groups such as
phenyl, tolyl, xylyl, and ethylphenyl, and aralkyl groups such as benzyl,
.beta.-phenylethyl, and .alpha.-methyl-.beta.-phenylethyl, with the aryl
groups such as phenyl being preferred. Letter m is an integer of 1 to 5,
especially 1 to 3.
The organopolysiloxane (A) preferably has a degree of polymerization (n) of
about 80 to about 1,200, especially about 100 to about 1,000. With n of
less than 80, the cured product of the composition has a high Young's
modulus and a low elongation. With n of more than 1,200, the composition
has a high viscosity and the organopolysiloxane becomes less compatible
with the monomer (B). Most preferably, the degree of polymerization (n) is
in the range of about 150 to about 500.
The organopolysiloxanes (A) can be synthesized by well-known acid
equilibration reaction. More particularly, they are synthesized through
acid equilibration reaction between a hexaorganodisiloxane having a
(meth)acryl group with various cyclic polysiloxanes. Of these disiloxanes,
bis(acryloxymethyl)-tetramethyldisiloxane is preferable for ease of
synthesis. Of the cyclic polysiloxanes, octamethylcyclotetrasiloxane,
hexamethylcyclotrisiloxane,
1,1-diphenyl-3,3,5,5-tetramethylcyclotrisiloxane, and
1-phenyl-1,2,2,3,3-pentamethylcyclotrisiloxane are used for ease of acid
equilibration reaction.
(B) Ethylenically Unsaturated Group-bearing Compound
Component (B) of the inventive composition is a compound having at least
one ethylenically unsaturated group in a molecule. Component (B) has a
function that it allows the composition to crosslink or cure by reacting
with the (meth)acryl group-bearing organopolysiloxane of component (A),
and thus is a component which is often referred to a reactive monomer or
reactive diluent. Illustrative are N-vinyl compounds and compounds of the
structure wherein (meth)acrylic acid is attached to compounds having an
amino or hydroxyl group by amidation reaction or esterification reaction.
For example, the following monofunctional, difunctional and polyfunctional
compounds can be used.
Monofunctional compounds:
Exemplary N-vinyl compounds are N-vinylpyrrolidone, N-vinylcaprolactam,
N-vinylacetamide, and N-vinylformamide. Exemplary compounds of the
structure wherein (meth)acrylic acid is attached to compounds having an
amino or hydroxyl group by amidation reaction or esterification reaction
are methoxyethylene glycol (meth)acrylate, methoxypolyethylene glycol
(meth)acrylate, nonylphenoxyethyl (meth)acrylate, nonylphenoxypolyethylene
glycol (meth)acrylate, nonylphenoxypolypropylene glycol (meth)acrylate,
3-chloro-2-hydroxypropyl (meth)acrylate, phenoxyethyl (meth)acrylate,
phenoxypolypropylene glycol (meth)acrylate, butoxypolyethylene glycol
(meth)acrylate, alkyl (meth)acrylates, cyclohexyl (meth)acrylate,
tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, benzyl
(meth)acrylate, cumylphenol (meth)acrylate, cumylphenoxypolyethylene
glycol (meth)acrylate, cumylphenoxypolypropylene glycol (meth)acrylate,
2-hydroxypropyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,
dicyclopentadiene (meth)acrylate, 2-hydroxy-3-phenoxypropyl
(meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxyethylphthalic acid,
3-acryloyloxyglycerin mono(meth)acrylate, 2-hydroxybutyl (meth)acrylate,
2-hydroxy-1-(meth)acryloxy-3-(meth)acryloxypropane, polypropylene glycol
mono(meth)acrylate, polyethylene glycol mono(meth)acrylate,
poly-.epsilon.-caprolactone mono(meth)acrylate, dialkylaminoethyl
(meth)acrylates, glycidyl (meth)acrylate,
mono[2-(meth)acryloyloxyethyl]-acid phosphate, trichloroethyl
(meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate,
2,2,3,4,4,4-hexafluorobutyl (meth)acrylate, perfluorooctylethyl
(meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyalkyl
(meth)acrylates, tricyclodecanyl (meth)acrylate, tricyclodecanyloxyethyl
(meth)acrylate, tricyclodecanyloxyethyl (meth)acrylate, isobornyloxyethyl
(meth)acrylate, and morpholine (meth)acrylate.
As the monofunctional compound having an ethylenically unsaturated group,
an acrylate compound containing a straight or branched organosiloxane
skeleton (that is, organic silicon compound) represented by the following
general formula (2) may be used. The use of this acrylate compound is
desirable because of the reduced change of Young's modulus at low
temperatures.
##STR2##
Herein R.sup.1 is a hydrogen atom or a methyl group, and a is equal to 0 or
1. Although R.sup.1 is a hydrogen atom or a methyl group, the hydrogen
atom is preferred when the curing rate of the composition upon exposure to
radiation is taken into account.
Difunctional compounds:
Exemplary difunctional compounds are di(meth)acrylate of
2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate, ethylene
glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate,
polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate,
polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate,
1,6-hexanediol di(meth)acrylate, glycol di(meth)acrylate, neopentyl
glycerin di(meth)acrylate, di(meth)acrylate of ethylene oxide adduct of
bisphenol A, di(meth)acrylate of propylene oxide adduct of bisphenol A,
2,2'-di(hydroxyethoxyphenyl)propane di(meth)acrylate, tricyclodecane
dimethylol di(meth)acrylate, dicyclopentadiene di(meth)acrylate, pentane
di(meth)acrylate, and (meth)acrylic acid adduct of
2,2-bis(glycidyloxyphenyl)propane.
Polyfunctional compounds:
Exemplary polyfunctional compounds are trimethylolpropane
tri(meth)acrylate, trimethylolpropane trioxyethyl(meth)acrylate,
pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate,
tris(acryloxymethyl) isocyanurate, tris(acryloxyethyl) isocyanurate,
tris-(acryloxypropyl) isocyanurate, triallyl trimellitic acid, and
triallyl isocyanurate.
Of these, the monofunctional compounds are preferred since the composition
of the invention is especially suited as the low Young's modulus primary
coating on optical fibers.
The amount of the compound having at least one ethylenically unsaturated
group in a molecule (B) blended is determined in accordance with the type
of (meth)acryl group-bearing organopolysiloxane (A) and compound (B), the
desired viscosity of the resin composition, and the desired physical
properties of a cured product thereof. For example, a choice may be made
in the range of about 5 to 200 parts, preferably about 10 to 150 parts,
more preferably about 20 to 100 parts by weight per 100 parts by weight of
(meth)acryl group-bearing organopolysiloxane (A).
(C) Photopolymerization Initiator
Any of well-known photopolymerization initiators may be used. Examples
include 1-hydroxycyclohexyl phenyl ketone,
2,2-dimethoxy-2-phenylacetophenone, phenylacetophenone diethyl ketal,
alkoxyacetophenones, benzyl methyl ketal, benzophenone and benzophenone
derivatives such as 3,3-dimethyl-4-methoxybenzophenone,
4,4-dimethoxy-benzophenone, and 4,4-diaminobenzophenone, alkyl
benzoylbenzoates, bis(4-dialkylaminophenyl)ketones, benzyl and benzyl
derivatives such as benzyl methyl ketal, benzoyl and benzoin derivatives
such as benzoin butyl methyl ketal, benzoin isopropyl ether,
2-hydroxy-2-methylpropiophenone, thioxanthone derivatives such as
2,4-diethylthioxanthone and 2,4-dichlorothioxanthone, fluorene,
2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1,2-benzyl-2-dimethy
lamino-1-(morpholinophenyl)-butanone-1, and phosphine oxide derivatives
such as 2,4,6-trimethyl-benzoyldiphenylphosphine oxide and
bis(2,6-dimethoxy-benzoyl)-2,4,4-trimethylpentylphosphine oxide.
Of these photopolymerization initiators, the phosphine oxide derivatives
are preferred for fast curing. The initiators may be used alone or in
admixture of two or more. The amount of the initiator used is usually
about 0.01 to 15 parts, preferably about 0.1 to 10 parts by weight per 100
parts by weight of components (A) and (B) combined.
In the resin composition of the invention, various additives, for example,
stabilizers such as antioxidants and UV absorbers, organic solvents,
plasticizers, surfactants, silane coupling agents, titanium coupling
agent, coloring pigments, and organic or inorganic particles may be used
if desired and insofar as the objects of the invention are not impaired.
The resin composition of the invention is prepared by blending the
above-described components and agitating and mixing them. The composition
is preferably adjusted to a viscosity of about 500 to about 10,000
centipoise at 25.degree. C. from the working standpoint for adapting
itself to usual manufacturing conditions of optical fiber cores and
especially about 500 to about 4,000 centipoise at 25.degree. C. for
adapting itself to high-speed manufacturing conditions.
Like conventional UV-curable compositions, the liquid resin composition of
the invention cures upon exposure to radiation, typically UV. The thus
cured coating should desirably have a Young's modulus of up to 0.1
kgf/mm.sup.2 in order to protect cores from microbending by external
forces and temperature changes. The type of radiation with which the
inventive composition is curable includes IR, visible rays, and UV as well
as ionizing radiation such as x-rays, electron beams, .alpha.-rays,
.beta.-rays and .gamma.-rays.
The radiation-curable liquid resin composition of the invention is not only
useful as optical fiber coatings, but also finds many other applications,
for example, as mold release coatings, water-repellent coatings,
protective coatings, various types of ink and paint.
The radiation-curable liquid resin composition of the invention is
especially useful as a primary coating on optical fibers. It is directly
applied to optical glass fibers to form a primary coating, over which a
secondary coating having a high Young's modulus is applied. The secondary
coating is typically a urethane acrylate composition which is a UV-curable
resin composition. The composition of the invention is also applicable as
a buffer or filler for water-proof fiber cables and submarine cable
optical fiber units.
EXAMPLE
Examples of the invention are given below by way of illustration and not by
way of limitation. All parts are by weight.
Synthesis Example 1
Synthesis of Acryl Group-bearing Organopolysiloxane (A)
A reactor was charged with 100 parts of
1,3-bis(acryloxymethyl)-tetramethyldisiloxane, 1,960 parts of
octamethylcyclotetrasiloxane, and 4,582 parts of
1,1-diphenyl-3,3,5,5-tetramethylcyclotrisiloxane. At 60.degree. C. , 7
parts of trifluoromethanesulfonic acid was added and equilibration
reaction effected for 24 hours. The reaction mixture was neutralized with
sodium bicarbonate, treated with activated carbon, and filtered. Volatiles
were distilled off at 150.degree. C. and 5 mmHg, yielding acryl
group-bearing organopolysiloxane (A) as shown below. It had a viscosity of
6,610 centipoise at 25.degree. C. and a refractive index of 1.4835.
Acryl-bearing organopolysiloxane (A):
##STR3##
It is noted that
##STR4##
units and
##STR5##
units are randomly distributed in the molecular chain.
Synthesis Example 2
Synthesis of Acryl Group-bearing Organopolysiloxane (B)
An acryl group-bearing organopolysiloxane (B) as shown below was
synthesized as in Synthesis Example 1, but using 100 parts of
1,3-bis(acryloxymethyl)-tetramethyldisiloxane, 3,430 parts of
octamethylcyclotetrasiloxane, 2,291 parts of
1,1-diphenyl-3,3,5,5-tetramethylcyclotrisiloxane, and 6 parts of trif
luoromethanesulfonic acid. It had a viscosity of 2,150 centipoise at
25.degree. C. and a refractive index of 1.4448.
Acryl-bearing organopolysiloxane (B):
##STR6##
It is noted that
##STR7##
units and
##STR8##
units are randomly distributed in the molecular chain.
Synthesis of Organosiloxane Compound (C) (a compound having an
organosiloxane skeleton and containing an ethylenically unsaturated group)
A reactor was charged with 652 parts of water, 327 parts of isopropyl
alcohol and 47 parts of 36% hydrochloric acid and cooled below 5.degree.
C. To this mixture, a mixture of 218 parts of
acryloxypropylmethyldimethoxysilane and 434 parts of trimethylchlorosilane
w as added dropwise while maintaining the reaction solution below
15.degree. C. After the completion of addition, the reaction solution was
stirred for 2 hours. The upper layer was separated off. The solution was
then washed with water, neutralized, dried over anhydrous sodium sulfate,
filtered, and distilled, yielding an organosiloxane compound (C) shown
below as a colorless, clear liquid. It had a refractive index of 1.4185.
Organosiloxane compound (C):
##STR9##
Examples 1-9 and Comparative Examples 1-2
Radiation-curable resin compositions of Examples 1-9 and Comparative
Examples 1-2 were prepared by mixing an acryl group-bearing
organopolysiloxane, an ethylenically unsaturated group-bearing compound
and a photo-polymerization initiator as shown in Table 1. The compositions
were examined for physical properties by the following tests.
Each resin composition was applied onto a glass plate to a build-up of a
thickness of 200 .mu.m. UV radiation having a wavelength of 350 nm was
irradiated to the coating in a dose of 500 mJ/cm.sup.2, obtaining a cured
film.
Young's modulus:
After the cured film was conditioned for 24 hours at 25.degree. C. and RH
50%, a 2.5% tensile modulus was measured under conditions: a gage mark
distance of 25 mm and a pulling rate of 1 mm/min.
Tensile strength and Elongation at rupture:
After the cured film was conditioned for 24 hours at 25.degree. C. and RH
50%, measurement was made under conditions: a gage mark distance of 25 mm
and a pulling rate of 50 mm/min.
With respect to outer appearance, the cured film was visually observed and
rated "O" when it was clear and "X" when it was white, opaque and
delaminated.
TABLE 1
Comparative
Example
Example
1 2 3 4
5 6 7 8 9 1
2
Composition (parts by weight)
Acryl-bearing 70 70 80 70
70 70 70 70 80
-- --
organopolysiloxane (A)
Acryl-bearing -- -- -- -- -- --
-- -- -- 70 70
organopolysiloxane (B)
Ethyleneically Nonylphenyl- -- 20 12 18
20 -- 15 15 -- -- 20
unsaturated polyethylene
group-bearing glycol-
compound acrylate*.sup.1
Nonylphenyl- 20 -- -- -- --
20 -- -- -- 20 --
polypropylene
glycol-
acrylate*.sup.2
Methyltri- 10 -- -- -- --
-- -- -- -- 10 --
ethylene glycol
acrylate
Isooctyl -- 10 -- -- --
-- -- -- -- -- 10
acrylate
Isobornyl -- -- 5 7
-- -- 5 -- -- -- --
acrylate
N-vinyl -- -- 3 5
-- -- -- 5 -- -- --
caprolactam
Organosiloxane -- -- -- -- 10
10 10 10 20 -- --
compound (C)
Photopolymerization 3 3 3 3
3 3 3 3 3
3 3
initiator*.sup.3
Properties
Outer appearance .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. X X
Viscosity (centipoise, 25.degree. C.) 1360 960 2100
1500 1550 1510 1260 1210 1210
UM UM
Refractive index n.sup.25.sub.D 1.4841 1.4822 1.4870
1.4879 1.4823 1.4811 1.4801 1.4819 1.4714
Young's modulus at 25.degree. C. 0.036 0.034 0.030
0.035 0.028 0.030 0.027 0.029 0.024
(kgf/mm.sup.2) at -40.degree. C. 0.046 0.15 0.10
0.17 0.039 0.037 0.059 0.067 0.034
Elongation at rupture (%) 168 238 178 175
212 228 195 215 230
Tensile strength (kgf/mm.sup.2) 0.034 0.037 0.031
0.040 0.043 0.063 0.031 0.036 0.036
*.sup.1 Aronix M-113 (Toa Synthetic Industry K.K.)
*.sup.2 Aronix M-117 (Toa Synthetic Industry K.K.)
*.sup.3 Irgacure 1700 (Chiba Speciality Chemicals K.K.)
The cured films of Comparative Examples 1 and 2 were white, opaque and
delaminated and their physical properties were unmeasurable ("UM" in Table
1).
There has been described a low-viscosity radiation-curable liquid resin
composition which cures into a product. having a low Young's modulus and
experiencing a less change of Young's modulus at low temperatures. The
composition is useful as a primary coating for optical fibers.
Japanese Patent Application No. 10-208656 is incorporated herein by
reference.
Although some preferred embodiments have been described, many modifications
and variations may be made thereto in light of the above teachings. It is
therefore to be understood that the invention may be practiced otherwise
than as specifically described without departing from the scope of the
appended claims.
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